[Purpose] There are three processes involved in an attentional shift: “disengagement” from the previous location, “movement” to, and “reengagement” on a new location. These processes are thought to be executed in serial order. The purpose of this study was to estimate the timings of “disengagement” and “reengagement” of attention from steady-state visual evoked potential (SSVEP). SSVEP is an oscillatory brain potential evoked by a continuously flickering stimulation and it has been shown that the attention modulates the amplitude and phase of the SSVEP. [Experiment] We recorded SSVEPs for two stimuli flickered at different temporal frequencies which were presented on the left and right sides of the fixation. Participants were instructed to either (1) stay their attentional focus on the same stimulus, or (2) shift attention toward the opposite side of the stimulus after the presentation of flashing cue adjacent to either of the stimulus. We measured the time course of SSVEP modulation under the two conditions: the condition where attention is kept on the stimulus throughout the trial and the condition where attention is shifted away at a certain time during the trial. From the time course data, we estimated latencies for the onsets of the disengagement and the reengagement of attention. [Results] The estimation of the timing of disengagement and that of reengagement showed that the attentional modulation of SSVEP involved in the reengagement process is faster in time than that involved in the disengagement process. This suggests that the two processes relating to attentional shifts are executed in parallel in the human brain, rather than that attention shifts from one location to the next in the serial processes.